The current US Open holder Kuznetsova got out to a fast start in the first set, but the heat and nerves contributed to her failing to hold in her last eight service games, ending the match with a double fault.

"It was just terrible," Kuznetsova said. "I was very focused and I play very well first set. And after something happened, so I just stopped. I mean, like my body was there, but my mind wasn't there at all. It was just, I don't know, ball boy playing out there."

Sharapova seemed most affected in the heat, taking time between points and leaning on her racquet for support.

"I was a bit lazy at the beginning of the match. I didn't run for as many balls," Sharapova said. "But the third set, end of the second set, is when I think both of us started feeling the heat and feeling tired and we wanted the points to go a lot quicker."

Mauresmo made 27 unforced errors against the American, struggling with her serve and an injured groin. Serena has beaten Mauresmo nine of the 10 times they have played.

"I think next time she plays me, she probably feels she has nothing to lose because I have such a good record," Serena said. "In a way it's like I have a bit of an advantage but at the same time she does too."